The most successful aerosol dispenser systems for spray application of products heretofore have been systems in which the propellant is present in a gaseous and liquid phase and the liquid propellant is commingled with the liquid product when under pressure in the container either by being miscible or soluble with or emulsified in the liquid product. The propellant is chosen to be one which rapidly vaporizes at ambient conditions. The static pressure provided by the propellant in the container forces the solution or emulsion of propellant and product through a discharge orifice when the dispensing valve is opened. At the discharge orifice the propellant rapidly vaporizes as the stream issues thereby assisting in breaking the stream into fine droplets of product which are essentially free of residual propellant.
The most common propellants used in spray systems are compounds of the chlorofluorocarbon type (hereafter fluorocarbons). Of late, these materials have been the focus of an environmental controversy regarding the adverse effect that said materials may have on the ozone depletion of the atmosphere. Because of the uncertainty of the impact of fluorocarbons on the so-called ozone layer, the aerosol industry must contend with the possible elimination of or a reduction in the reliance upon these materials as useable propellants. While non-fluorocarbon liquid propellants are available, namely, certain hydrocarbons such, for example, as propane butane and isobutane, their use with solvent-based products, such as alcohol, have presented flammability problems. These flammability problems can be alleviated by the use of aqueous systems, with the propellant present as a separate liquid phase or as an emulsion, but prior dispensing systems of that type require high percentage of propellant and have not provided the desired spray characteristics. The problem has to do with large and uneven droplet size and an unacceptably slow drying rate. Thus, in a system wherein the propellant and product are essentially immiscible there is a pressing need for a dispenser that will produce a spray having characteristics similar to that achieved by soluble propellant product systems.
In systems employing an insoluble propellant, resort has been made to mechanical means for effecting a break-up for finer dispersion of the product. For example, a common mechanical means is the disposition of a chamber at or near the discharge orifice to centrifugally swirl the product before discharge. Also, dispensing valves having vapor taps or ports in communication with the propellant vapor present in the head space of the container serve to assist the mechanical break-up by introducing propellant vapor into the product stream prior to entering the swirl chamber. In the case of insoluble systems, generally, the spray characteristics such as small droplet size, uniformity of distribution, and pattern of a mechanically created spray are inferior to those of a soluble system spray.
Another approach to dispensing products as a fine dispersion under conditions such that the propellant is not soluble in the product, is to employ the venturi principle, as shown in my U.S. Pat. Nos. 3,326,469 and 3,437,272. Product and propellant are kept in separate containers, with the product stored under atmospheric pressure and the propellant at a different but considerably higher pressure. A stream of propellant gas, by virtue of the Bernoulli effect, creates a vacuum which draws the product to a venturi device where the product stream is sheared into droplets as it meets the propellant stream. Such venturi spray devices can give many acceptable spray characteristics, but the handicap of such venturi spray devices is the need to keep product and propellant in different containers, making the handling of product and system more complicated for producers and customers. There are no known valved aerosol dispensers providing simultaneous and separate release of product and propellant from a single container to a dispersing outlet, wherein the product and propellant are in contact within the container; and further wherein the valve and actuator are disposed in or contiguous to the container closure member.